Reported sexual abuse is rising in prisons and jails across the U.S. Most inmates accuse guards inflicting the crime than other captives.

A study released Thursday by the U.S. Justice Department’s Bureau of Justice Statistics (B.J.S.) estimated that 88,500 adults imprisoned or jailed experience sexual abuse from guards and other inmates, Dan Froomkin reported today at The Huffington Post. “It’s up a bit from the previous estimate of 85,200, based on separate 2007 surveys of prisons and jails,” he added.

The study found 4.8% of prison inmates and 3.1% of those in jails reported being sexually victimized, based on a 2009 survey in the report. Most reports accused guards of the abuse.

2.8% reported being sexually abused by guards, compared to 2.1% who reported being abused by other inmates. “The staff statistics include ostensibly willing sexual activity, as all sexual contacts between inmates and staff are legally non-consensual,” Mr. Froomkin reported.

Most accusations against staff identified females guards in men’s facilities as perpetrators, while most inmate-on-inmate abuse was reported in women’s facilities.

“Female inmates in prison (4.7%) or jail (3.1%) were more than twice as likely as male inmates in prison (1.9%) or jail (1.3%) to report experiencing inmate-on-inmate sexual victimization,” the B.J.S. report stated.

The study did not include juvenile facilities, but Mr. Froomkin added that “in a similar B.J.S. report released in January, more than 12 percent of youth in juvenile detention—or one in eight—reported sexual abuse; again, mostly by facility staff.”

The Pew Research Center estimated [.pdf] the state and prison population in the U.S. at over 1.6 million incarcerated at the end of 2009. In July 2009, the Bureau of Prisons reported [.pdf] a 4.9:1 inmate-to-staff ratio in the system.